Automatic control mechanism for empty and load brakes



NOV 7', 1939. B BRQWALL 2.173399 AUTOMATIC CONTROL MECHANISM FOR EMPTY AND LOAD BRAKES Filed Nov. 30, 1937 3 Sheets-Sheet l 3H P fi0 am/n 35 I 33 a u /wwwf' NW4, 7, W39. B. H. BROWALL AUTOMATIC ONTROL MECHANISM FOR EMPTY AND LOAD BRAKES Filed Nov. 30, 1937 5 Sheets-Sheet 2 Wm W W Wm WW W MWm WEWm NOV. 7, 1939. BROWALL 2.179.399

AUTOMATIC CONTROL MECHANISM FOR EMPTY AND LOAD BRAKES Filed Nov. 30, 19:57 s Sheets-Sheet s Patented Nov. 7, 19 39 AUTOMATIC CONTROL MECHANISM FOR EMF-TY AND LOAD BRAKES Bert Henry Browall, Malmo, Sweden, assignor to Svenska Aktiebolaget Bromsregulator, Malmo,

Sweden, a ccrporation of Sweden Application November 30, 1937,Serial No. 177,334

' lin Germany December 3, 1936.

7 claim 01; 188 195) This invention relates to brake apparatus-for vehicles, andmore particularly to such-brake apparatus in which. 'thebrakes are applied with greater iorceon loaded cars than on empty cars.

The principal object of theinvention is to provide means. automatically operative to condition the brake apparatus for empty I car operation or for loaded car operation in accordance wlth variations in the weight of. the load. on the vehicle. l

A further object of the invention is tolprovide automatic control meansforempty and load brake equipments, operatingdn. dependence not only of theweight but also oithe distribution of Weight of the load: on the vehicle.

Another object of the invention is; to provide an automatic control means for empty: and load brake equipments and incorporatingtmeansfor preventing the brake equipment being conditioned for loaded car. operationlashlong. as the amount of load carriedat any end of the vehicle isbelow a predetermined .value calculated to eliminate the. risk. of sliding the wheels at that end under full. brake application; 1;

Other objects of the invention and. features of novelty, residing in advantageous forms,l.combinations and relations of parts, will. be apparent from the following description taken. in. connection with the. accompanying drawings in. which-.

Fig. l is a diagrammatic side view, partly in section, of one embodiment oii the. invention:

Fig. 2 is asimilar view of: asecond embodiment of the invention. i I

Fig. 3 is a section on a larger.scaleofsavalve arrangement in the embodiment of Fig. 2..

Fig. 4 is a diagrammatic side view, partly in section, of a third embodiment of the invention. Fig. 5 is a section: on a larger scale of a. valve arrangement in the embodiment of Fig. 4.

Fig. 6 is a. diagrammatic side view,. partly in section, of a fourth embodiment of the invention. Fig. 7 is a section on a larger scale of. a valve arrangement in the embodiment of. Fig; 6.1.

Fig. 8 is a diagrammatic View, partly in section,

lever into, and maintain itin, engagement .with the upper abutment Eaor. 5b, respectively. For each lever there is further provided a cylinder 6a or 6b, respectively, in which a piston la or lb,

respectively, is movable, which when. the respective cylinder is put in operation tendstomove the lever towards, and to hold it against, the lower abutment 'ta. or 411, respectively. The cylinders 6a and 5b are both connected to a. conduit Ill leading from a pressure fluid reservoir l l to a servomotor 9; This pressure fluid reservoir. I l .-is connected through anonrreturn valve 12 to the main brake pipe 8. Between the two cylinders. 6a and 61) there. is provided in the conduit Ill. a three- Way Valve ltd which is connected by means ofv a link rodllda. or the like with the lever 2a at one end of. thecar and is operated thereby. When this. lever Zaxengages the lower abutment lwthe three-way valve lid closes the conduit ill between. the cylinder to. and the cylinder 6b and. vents. the cylinder lib through a port l5a to the atmosphere. When the lever 2a engages the .upper. abutment 5av the three-way valve I30. closes the port 115a. to theatmosphere and opens its inlet port or passage for pressure fluid to the cylinder .Bb through the conduit ill. Between the cylinder three-way valve Nib-closes the conduit It between thecylinder 6b and the servomotor 9 and vents the latter through a port i511 tothe atmospheres: When the lever 2b engages the upper" abutment 5b the three-way valve l3b closes the port l5b-to the atmosphere and opens the con.- duit ill. to the servomotor 9. Pressure fluid. from reservoir. l I being now admitted to the servomotor, the latter by means of :ashifting member (not shown) connected thereto at l6 shifts the brake to the higher braking effort condition and holdsthe brake in this condition as long as the admission of pressure fluid is continued. When this supply of pressure fluid is discontinued and the servomotor is vented to the atmosphere, the servomotor piston returns to its starting position through the action of a spring ll, the brake being, thereby reset to the lower braking effort condition. As a matter of course, the return of the servomotor piston to the starting position corresponding .to the lower braking effort condition may also take place through the action of fluid pressure, but the use of a return spring affords, from, the point, of view of safety, theadvantage that the starting condition of the brake always will be that corresponding to the lower braking elTort and that the return to this starting position will take place also when no fluid pressure is available. Besides, if the servomotor is to be operated by fluid pressure in both directions, a more complicated valve arrangement and a larger number of conduits and connections will be required, as is to be seen from the example diagrammatically shown in Fig. 8. When in the embodimentaccording to Fig. l the load carried by the Wheel a? e a is insufficient to move the lever 2a to the upper end position against the action of the fluid under pressure on the piston la the admission of fluid under pressure to the cylinder 6b and to the servomotor 9 is shut oif, and the cylinder 6b as well as the servomotor are vented to the atmosphere through the port 55a, the piston lb always allowing the lever 21), as soon as the pressure in the cylinder tab is released, to take the upper end position in which the three-way valve l3b establishes communication between the servomotor and the cylinder 31). When, on the other hand,

the load carried by the wheel axle a is sufficient to move the lever 2a to the upper end position, the three-way valve lEla will be shifted so that fluid under pressure will have admission also to .the cylinder Eb. If now, however, the load carried by the wheel axle b is not sufiicient to hold the lever 21) in the upper end position against the action of the fluid pressure on the piston lb, the lever 21) will at once be moved into the lower end position, the three-way valve |3b being thereby shifted so that the admission of pressure fluid .to the servomotor 9 is shut off and the latter is instead vented to the atmosphere through the port i527. Thus, also in this case the servomotor will not be actuated so that a shifting of the brake to the higher braking effort condition does not take place. If, on the other hand, the load on the wheel axle 12 would be sufficient to hold the lever 2b in the upper end position against the action of the fluid pressure on the piston lb, the

pressure fluid will have free admission to the servomotor and this performs the shifting of the brake to the higher braking efiort condition. Thus, shifting of the brake to the higher braking eflort condition will take place only in case both the load carried by the wheel axle a and the load carried by the wheel axle b exceed the predetermined limit above which the risk of causing the wheels to slide if braked with the brake in the higher braking effort condition is eliminated to a satisfactory degree.

In the embodiment shown in Fig. 2 each lever 2a and 2b is associated with a valve housing I and i811, respectively. This housing is identical for both levers and is shown separately in Fig. 3 where it is generally designated by I8. This valve housing is secured to the car frame by means of bolts l9. It contains an upper chamber 20 which is tightly sealed at the top by a diaphragm 22 fixed between the housing and a cover 2| mounted thereon, the diaphragm carrying a pin 23 projecting through a central opening in the cover 2| against which pin the lever 2a or 21), respectively, is resting. The lever 2a or 217-, respectively, tends through the action of the load carried by the corresponding wheel axle to hold the diaphragm 22 and the pin 23 pressed down in the lower position. The chamber is preferably filled with a damping fluid and communicates with a chamber 24 located under the same in the housing l8 preferably through a restricted port 25 and a tube 26 projecting downwards from said port into the chamber 24 near to the bottom thereof. The chamber 24 which preferably is partly filled with damping fluid is connected through a connection member 21 to a conduit 28 leading to the pressure fluid reservoir connected to the brake pipe 8 through the nonreturn valve l2. Between two further chambers 29 and 30 in the housing |8 there is provided a valve 3|, this valve 3| and a valve 32 which controls a port between the chamber 30 and the atmosphere being controlled by the diaphragm 22 by means of a spindle 34 connected with the latter in such a manner that the valve 3| is closed, the valve 32 on the other hand being open, when the diaphragm 22 is held in its upper end position, whereas the valve 32 is closed, and the valve 3| open, when the diaphragm is pressed into its lower end position. The spindle 34 is tightly but slidably mounted in a bore in the wall between the chambers 29 and 30 in the housing l8, and the valve 32 is, for example by means of a link 35, connected with a lever 39 pivotally mounted on the valve 3| and engaging in a recess at the lower end of the spindle 34. The chamber 29 is provided with a connection member 3l and the chamber 39 with a connection member 38. The connection member 31 of the valve housing E80. is connected by conduit 39 with the conduit 28, .as shown in Fig. 2. The connection member 38 of the valve housing la is connected through 2. iii

conduit 46 with the connection member 31 of the valve housing I819, and the connection member 38 of the valve housing |8b' communicates through a conduit 4| with the servomotor 9.

The diaphragm 22 with the pin 23 is pressed to downwards against the pressure exerted by the corresponding lever 2a. or 219, respectively on the under side of the diaphragm, only in case the load carried by the corresponding axle exceeds the limit above which the risk of causing the wheels on said axle to slide if braked with the brake in the higher braking effort condition is practically eliminated. If the diaphragm 22 is pressed down only in the housing |8a but not in the housing |8b fluid under pressure is carried through the chambers 29 and 30 of the housing I811. to the chamber 29 of the housing |8b but in the latter the valve 3| is closed and the valve 32 open, so that the pressure fluid is not allowed to reach the servomotor 9 and the fluid therein 1.

is vented to the atmosphere through the open valve 32 in the housing |8b. When the diaphragm 22 of the housing |8b but not that of the housing i811. is pressed down in its lower position, the admission of pressure fluid to the servomotor is blocked by the closed valve 3| of the housing l8a, and the servomotor is vented to the atmosphere through the chambers 39 and 29 of the housing I81) and through the open valve 32 of the housing lad. Only when the diaphragm 22 is pressed down at the same time in both housings IBa, and |8b will pressure fluid be supplied to the servomotor 9, so that the brake is shifted to, and maintained in, the higher braking effort condition.

In the embodiment shown in Fig. 4 the two levers 2a and 2b both together serve to operate a valve common to both of them in such a manner that said valve will allow admission of pressure fluid from the brake pipe 8, or the pressure fluid reservoir II, to the servomotor 9 only when the load at both wheel axles exceeds the limit above which the risk of the wheels being slid if braked with the brake in the higher braking effort condition is practically eliminated, but under surfaces) both sides by diaphragms43a: and 4327. In engagement with. the diaphragms there, are provided two stems. 55a and 45b which are slidable within predeterminedylimits in the end: of the housing and which are connected through levers Mia and liib as well as through connecting rods Ma and llb with the levers 2a; and 2b; The levers Mia. and Mia arepivotedto link. members ite and till) which are pivotably mounted? on ears providedeon thehousing, 42. The chamber 44 is connected through aconduit 49 with thereservoir l-l connected by thenon return valve. 12 to the brake pipe ii. In abore 55 a valve slide 5,! is tightlybut slidably mounted. which in its upper portion is providedwith a slot 52 in which two coacting wedges 'i3anand 53?) connected each with oneofthe diaphragmsfiiia and 431) are located. From the chamber M a channel 54 leads through the slide, 5| and opens in its peripheral surface as shown at 55 in Fig; 5, and more particularly belowua circumferential groove 56 provided in the slide. Within the bore 50 a circumferential groove 5'! is provided which is connected by means of a, connecting member 58 with a conduit 53' leading totheservo-motor. If the slide 5L takes the position showninFig. 5 the circumferential groove 56 communicates with-the circumferential. groove 57 and a port 69 opening in the boring andleading to theatmosphere. From the bottom end of the boring; 50 a port 6| leads .to the atmosphere.

If the loads carried by the wheel axles a and b simultaneously at bothaxles exceed the predetermined limit so thatthe two stems 45a and thbare simultaneously{moved to their inner end positions against, the substantially constant pressure ini-thechamber M acting on the, diaphragm, theewedges 53a and. 53b will be moved towards-each other soas to lift the slide 5!,

whereby Athe connection between the circumferential grooves fifiiand ii! is broken off and the opening, of the, channel 5t brought, to communicate with the groove} 5'1 and theconduit- 5t tothe servoj motor, so that the brake is shifted tothe higherbraking effort condition. If, on the other hand, the predetermined load limit is not reached atkone. of thewheel axles a: or b, so that one of the stems 25a; and 451) under the actionofthe pressure in the chamber id is in the outer end position; the slide will not, whatever the positioneoccupied by the stem, be lifted in the manner described above, so that no pressure fluid is supplied toitheservomotor and the latter relnains vented to the atmosphere through the conduit 59, the-grooves .i'l and 5s and the port fill, in the embodiment according toFig. 6 the levers 2d and Zhare eachbyjmeans of links 62a and 55% connected with one end of afioating lever 63 which is journaled at the centre in the pistonrod lid of a piston 65 which is movable in a cylinder M, The cylinder chamber above the piston communicates through a conduit 61 with the prcssure fluid reservoir Ii connected through the non-return valvev I2 to the brake pipe t, while the cylinder chamber below the piston th is vented tothe atmosphere through a port 68. As isbest showninFigl 7 which illustrates thecylinder 65, the piston til and the piston rod 36 in detail, the pistonrod M is formed as a slidegvalve and for this, purpose provided with a. channel 69 which in the lower end position of the piston connects a circumferential groove located within the piston rod guide with the cylinder chamber located below the piston 65, and further with a channel (I which in the upper end position connects the circumferential groove 10 with the cylinder chamber located above the piston 65, The servomotor 9 ,is connected by means of a conduit 12V to the groove 10.

Each lever 2a and 21), independently of its position,is loaded by half the force of the piston 65. If one of the levers 2a, 2b-against the action of the forceexerted thereon by the piston 65 through the floating lever 83 is transferred into its upper end position, i. e., into engagement. with the upper abutment 5a or 5b, respectively, the piston will be displaced only half-way towards the upper end position, and the arrangementis chosen so that the servomotor in this case remains vented to the atmosphere through the conduit 12, the groove 10, the channel 69, the cylinder chamber below the piston 65 and the port 68. Only when .the two levers 2a and. 2?) at the same time are in their upper end positions the piston 65 will occupy its upper end position in. which the circumferential groove 10 and thereby also the servomotor Flare shut off from the atmosphere and are supplied with pressure fluid through the channel H from the cylinder chamber above the piston 65, so that the brake will be shifted to, and held in, the higher braking effort condition.

Inthe embodiment shown in Fig. 8, where the return of the servomotor piston to the end position corresponding to the lower braking effort condition is to be effected not by means of a spring but by means of pressure fluid, the valves which control the admission of pressure fluid to the servomotor and the venting of the latter to the atmosphere, instead of three-way valves consist of slide valves 73a and 13b connected with the levers 2a and 2b, respectively, at the opposite ends of the car and adapted to cover ports opening into pressure fluid chambers Ma and 74b, respectively, connected to the pressure fluid conduit Ill and the pressure fluid reservoir I! (Fig. 1), or to interconnect and to vent said ports to the atmosphere through the recesses a, 16a and 15b, 76b, respectively. Theslide valves 73a, 1319 are connected with the levers 2a and 2b, respectively, in such a manner that ingly remain in the end position corresponding to the lower braking effort condition, always are in'the upper position as shown in Fig. 8, whereas they, as soon as the load on the wheel axles exceeds the predetermined limit, are moved by the respective levers 2a and 2bto the lower end postion corresponding to the higher braking effort condition indicated by dash and dotlines. In the lower braking effort condition the piston of the servomotor is in the left hand end of the servomotor cylinder 9 as shown in Fig. 8, while in the higher braking effort condition it is in the right hand end of the cylinder. When both slide valves 13a and 1313, due to the load on the two wheel axles a and 12- being below the predetermined limit, are in the upper end position, as shown in Fig. 8, the right hand end of the servomotor cylinder 9 is connected by the conduits TI and 18 with the pressure fluid chambers Ma and Mb, while the left hand end of the'servomotor cylinder is vented, on the one hand, through-itheconduit T9, the recesslfia in. they slide 13a and the conduit 80 and, on the other hand, through the conduit 81, the recess 15b in the slide 73b and the conduit 82 to the atmosphere. Thus, when both slide valves'occupy the upper end position the servomotor piston will be held by fluid pressure in the left hand position corresponding to the lower braking efiort condition. If now the load on the wheel axle it exceeds the predeterminedllimit, and the slide valve 73a is thereby moved into its lower end position, whereas the slide valve 131), due to insufficient load on the wheel axle b, remains in the upper end position, the right hand end of the servomotor 9 communicates through the conduit 'H and the right hand portion of the conduit T8 with the pressure fluid chamber Mb, while the left hand branch ofthe conduit '18 is connected through the recess 76a in the slide valve 13a with the conduit 83 which, however, is shut off by the slide valve 13b. The right hand end of the servomotor is thus subjected to fluid pressure. The left hand end of the servomotor is thereby vented through the conduits is and M, the recess 'l5b in the slide valve 131) and the conduit 82, while theportion of the conduit 19 opening towards the chamber Ma is connected through the recess 15a in the slide 130: with the conduit 84 which, however, is shut off from the chamber 141) by the slide valve 13b. The left hand end of the servomotor is thus vented to the atmosphere, and the servomotor piston is still held in the left hand end position corresponding to the lower braking effort condition. If now the force acting on the wheel axle it comes short of the predetermined load limit and the slide valve 13a accordingly takes the upper end position, whereas the slide valve 531) takes the lower end position due to the higher load on the wheel axle b, the pressure conditions of the servomotor remain unchanged, the right hand end of the servomotor being connected through the conduit Ti and the left hand branch of the conduit 1'3 with the pressure fluid chamber I la, while the right hand branch of the conduit i8 is shut off by the slide valve 732). The left hand end of the servomotor is vented through 19, 15a and 86, while the conduit Bl is shut off from the chamber 'l ib by the slide valve i311. In this position the servomotor will also occupy the position corresponding to the lower braking effort condition. If both slide valves 13a and 13b, due to the loads on both the wheel axles a and b exceeding the predetermined load limit, are in their lower end positions, the right hand end of the servomotor 9 will be vented through the conduits l1 and T8, the recess 16a in the slide 13a, the conduit 83, the recess 15b and the conduit 85, while the left hand end of the servomotor 9 communicates with the pressure fluid chamber Mb through the conduit 19, the recess 15a in the slide valve 13a and the conduit 84 which is left open to the chamber Mb, the slide 53b being in its lower end position. Thus, only in this case when both slide valves 63a and it?) are in their lower end positions due to the load on both the wheel axles a and b exceeding the predetermined limit, will the left hand side of the servomotor piston be supplied with pressure fluid and the brake shifted to the higher braking effort condition.

The invention is not confined to the embodiments described above and shown in the drawings for the purpose of illustrating the invention only. For example, it is preferable but not always necessary to use a servomotor, the shifting of the brake, being if desired performed directly for example by means of the slide or the piston 64 in the embodiments shown in Figures 4 to 5 and 6 to 7, respectively. To derive the forces proportional to the fractions of the car load carried by the respective wheel axles it is possible to use other means instead of the levers 2a and 2b as shown, for example oil pressure pots operated by the car spring reaction and pistons, diaphragms or the like acted upon by oil pressure in said pots. Also in other respects the constructional features of the apparatus may be varied within Wide limits without departing from the mode of operation which is common to all of the forms of invention illustrated.

What I claim and desire to secure by Letters Patent is:

1. In combination with an empty and load brake equipment for a vehicle, an automatic mechanism for controlling the conditioning of the brake for empty or load operation, comprising members movable between two opposite positions, such members being disposed at both ends of the vehicle and each arranged to be actuated by the load resting on the corresponding end of the vehicle so as to take one of its positions when the vehicle is empty and the opposite position when said vehicle end is loaded, servomotor means for executing the shifting of the brake into empty or load operating condition respectively, and means interconnecting the movable members and the servomotor means, said interconnecting means being so arranged as to cause the servomotor means to keep the brake conditioned for empty car operation as long as any of the movable members takes its position corresponding to empty car, and to condition the brake for loaded car operation only when all of the movable members take the position corresponding to loaded car.

2. In combination with an empty and load brake equipment for a vehicle, an automatic control mechanism for the conditioning of the brake for empty or load operation, comprising load influenced controlling members at both ends of the vehicle, said controlling members being arranged in series so that load operation of the brake can take place only when all of the controlling members are in load position.

3. In combination with a vehicle brake of the type which is adapted to be set either in a lower or in a higher braking effort condition by a member shiftable from one to the other of two positions corresponding to the lower and the higher braking effort condition of the brake respectively, an arrangement for controlling said shiftable member automatically according to the load of the vehicle carried on supporting springs 'at both ends thereof, comprising movable members disposed at both ends of the vehicle and arranged to take different positions independently of each other according to the load values transmitted through the supporting springs of the vehicle at the respective ends thereof but independently of the vehicle supporting spring deflection caused by said load, and means connecting said shiftable member to said movable members so that each of said movable members is capable not only of preventing the shiftable member from being shifted from the lower to the higher braking effort position until the value of the load transmitted through the supporting springs of the vehicle at the respective end thereof exceeds a predetermined limit, but also of causing the said shiftable member to be shifted back to the lower braking effort condition as soon as the value of the load transmitted through the supporting springs of the vehicle at the respective end thereof is again reduced below said limit.

4. An arrangement as claimed in claim 3, in which the shiftable member is arranged to be actuatedby a pressure fluid operated servomotor controlled by valves each of which is operatively connected to one of the movable members and controls an inlet port and an outlet port in a pressure fluid supply conduit to the servomotor, and in which said valves are arranged in series in said conduit so that the pressure fluid for admission to the servomotor for causing it to shift the brake from the lower to the higher braking effort condition must pass through the inlet ports of all the valves in succession, the inlet and outlet ports of each valve being so arranged that when the inlet port is closed the outlet port is opened and allows escape of pressure fluid from the conduit extending from the valve towards the servomotor.

5. An arrangement as claimed in claim 3, in which the movements of the movable members are summed up on a common control member for the shiftable member, and in which said control member is so arranged and related to the said shiftable member that the latter is set in the higher braking effort position only when said control member is in an end position which it takes only when all the movable members are in the position into which each of them is moved independently of the other when the load at the respective end of the vehicle exceeds the predetermined limit, the shiftable member being set in the lower brakingeffort condition in all other positions of the said control member.

6. In combination with an empty and load brake equipment for a vehicle, an automatic control mechanism for conditioning the brake for empty or load operation, comprising load influenced controlling members at both ends of the vehicle, each of said controlling members being movable, independently of the other, into either of an empty position and a load position, and each capable, likewise independently or the other, of setting the brake into the empty operating condition, namely when moved from the load position to the empty position, so that the brake will be in the load operating condition only when both the controlling members are in the load position.

7. In combination with an empty and load brake equipment for a vehicle, an automatic control mechanism for conditioning the brake for empty and load operation, comprising a pressure fluid operated servomotor for shifting the brake from the condition for empty operation. to the condition for load operation and vice versa, a pressure fluid supply conduit for said servomotor, and load influenced members at both ends of the vehicle for controlling the operation of said servomotor, said controlling members being movable, independently of each other, into either of an empty and a load position, and arranged in series in said pressure fluid supply conduit so as to render said servomotor operative for shifting the brake to, and maintaining it in, the condition for load operation only when, and as long as, the controlling members at both ends of the vehicle take the load position.

BERT HENRY BROWALL. 

